Add Pebble App/Watchface locker to Pebble App

[raketti]

There's now no way of reinstalling watch faces or apps, if one has to reset the phone or reinstall the Pebble App for some reason. The apps/faces in the Pebble App Store cannot be added again, there's only a grey button displaying Added.

I noticed that the Android version of the Pebble App stores the installed apps/faces to a place called locker from where the user can later reinstall the downloaded apps. And these are stored behind the user's Pebble account, so it doesn't matter if you change the phone, reinstall the App - they're stored and easily available to be installed again.

There is a library of installed apps/faces on the Sailfish version of the Pebble App, but it's cleared if the App is uninstalled or the phone is reset. It would be nice to have the same functionality as the Android App has.

[abranson]

I think this should also enable pebble app upgrades, but sounds like a lot of work with undocumented interactions with pebble's server.

[smurfy]

I already implemented locker add and fetching the locker but did not have time implementing more at the moment